The present invention relates generally to engine starters and generators and, more particularly, to combined engine starter/generators.
In the aerospace industry, electric engine start technology has become a de facto standard for engine starters and generators. According to an aspect of this technology, a starter and a generator may be combined in a single starter/generator device. Such a design may be advantageous in terms of weight and size.
A starter/generator device may include three generators: a permanent magnet generator, an exciter generator, and a main generator. Each generator may include a stator and a rotor. Each rotor may include a winding.
A starter/generator device may be a synchronous, brushless electric device. A starter/generator device may be said to be synchronous when the frequency of the starter/generator device is proportional to an input speed when the starter/generator device is in a generate mode. A starter/generator device may be said to be brushless when, instead of using brushes to transfer current to main rotor, an exciter may be used to provide excitation current to the main field when the starter/generator device is in a generate mode.
In order to effectively start an engine, torque is necessary. When a conventional starter/generator device is placed in a start mode, a start controller unit may be used to provide electrical power to create torque of the starter/generator device. The start controller unit may add significant weight and volume to a starting system. Depending on the application, the start controller unit can range, for example, from 50% to more than 100% of the weight of the generator itself. Additionally, the starter/generator device may be located at a distance from the start controller unit requiring unwanted additional wiring.
As can be seen, there is a need for an aircraft engine starter/generator device not requiring a start controller unit.